Flame detector control means for a burner assembly



Dec. 31, 1968 G. J. FAIRBANKS 3,419,337

FLAME DETECTOR CONTROL MEANS FOR A BURNER ASSEMBLY Filed July 28, 1967 j I 7108712 671- 50 94 10/ 26 74 GamZmJFu'rbanka United States Patent 3,419,337 FLAME DETECTOR CONTROL MEANS FOR A BURNER ASSEMBLY Gordon J. Fairbanks, Indianapolis, Ind., assignor to Stewart-Warner Corporation, Chicago, 111., a corporation of Virginia Filed July 28, 1967, Ser. No. 656,917

3 Claims. (Cl. 431-77) ABSTRACT OF THE DISCLOSURE A control device which comprises switch means actuatable by temperature responsive flame detector means and which is mounted at the combustion air intake end of an air-fuel mixer casing of a burner assembly.

Background of the invention Field of the invention.-The present invention pertains generally to a burner assembly for a vehicle heater or the like, and more particularly to flame detector control means for such a burner assembly.

Description of the prior art-In one type of vehicle heater, as disclosed in United States Patent No. 2,990,877, a burner assembly, comprising a cup-shaped air-fuel mixer casing, is mounted in one end of a heat exchanger. Combustion air and fuel are supplied from suitable sources to the mixer casing at one end, the combustible mixture is spark-ignited, and hot products of combustion are discharged from the other end of the mixer casing to the interior of the heat exchanger from which the heat is exchanged to a ventilating air stream.

Usually a control device is provided to detect the flame within the air-fuel mixer casing. The control device is used to actuate safety means that stops the flow of fuel in the event the flame goes out and also to provide a purge period by accommodating operation of the combustion blower for a short period of time after the flame has been turned off. Heretofore, such control device has been mounted at the side of the burner assembly with temperature responsive flame detector means projecting generally radially into the mixer casing. This arrangement has required seal means for the control device by reason of the location of the latter in the vicinity of the combustion gases.

Summary of the invention In accordance with the present invention, the flame detector control device is mounted at the combustion air intake end of the air-fuel mixer casing with the temperature responsive flame detector means projecting axially into the mixer casing. With this arrangement, no seal means is required at the mounting of the control device in the mixer casing. Thus, the burner assembly is simplified in design, is more compact in construction, and is more economical to fabricate and assemble.

Brief description of the drawing in FIGURE 1, looking in the direction indicated by the arrows.

3,419,337 Patented Dec. 31, 1968 Description of the preferred embodiment Referring now to the drawing, there is indicated generally by the reference numeral a burner assembly for a vehicle heater or the like. The burner assembly 10 comprises a generally tubular cup-shaped air supply casing 12 which may be die cast and which has a closed end base 14 and a peripheral flange 16 at the open end. The base 14 is formed with a central hollow stem 18. In a conventional manner, a fuel spray nozzle 20 is secured in the end of the hollow stem 18, the elements of a magnetically actuated poppet type fuel valve 22 are mounted within the stem 18, and a solenoid 24 for actuating the valve 22 is secured to the base 14. The casing 12 is also provided with a lateral tubular horn 26 through which air for combustion may be introduced into the casing.

A transverse circular metal plate 28 is secured, by means of screws 30, to the air supply casing 12 across the open end or mouth thereof. The plate 28 is formed with a central opening 32 through which the outer end of the fuel spray nozzle 20 projects, and with a plurality of apertures 34 spaced circumferentially around the central opening 32. The plate 28, adjacent the outer peripheral portion, is lanced and deformed to provide air passageway means in the form of a plurality of circumferentially spaced louvers 36. The apertures 34 and louvers 36 accommodate the flow of combustion air outwardly of the casing 12 in a manner to be more fully described hereinafter.

Extending coaxially of the air supply casing 12 is a generally tubular sheet metal cup-shaped air-fuel mixer casing 38 of smaller diameter than the air supply casing 12. The casing 38 has a base 40 which is secured to the central portion of the plate 28 by means of rivets 42, with the louvers 36 located radially outwardly of the casing 38. In order to space the casing 38 slightly from the plate 28, the rivets 42 are secured through stamped bosses 44 formed either in the plate 28 or the base 40 or both. The base 40 is further provided with a central inwardly flanged opening 46 that surrounds the fuel spray nozzle 20, and with a plurality of combustion air passageway means or inlet holes 48 in the side wall thereof. The outer open end or mouth of the casing 38 is flared outwardly to provide a cylindrical flange 50, and extending across the open end of the casing 38 is a narrow metal strip 52 which serves to effect desirable turbulence within the casing 38.

The air-fuel mixer casing 38 is surrounded by enclosure means which may, for example, be in the form of a tubular burner adapter fitting 54 having flanged end portions 56 and 58. The flanged end portion 56 has a loose sliding fit with the flange of the casing 38, While the flanged end portion 58, the flange 1 6 of the casing 12 and an intermediate resilient sealing gasket 60 are secured together by a screw tightened split peripheral clamping band 62. The fitting 54 serves to define an annular chamber 63. Extending through aligned openings in the base 14 of the casing 12, the plate 28 and the base 40 of the casing 38 is -a spark plug 64 having an electrode 66. The insulator body of the spark. plug 64 is secured and sealed in the base 14 by a screw-held clamp fitting 68 and copper gaskets 70. The electrode 66 projects into the air-fuel mixer casing 38 in close proximity to a grounded electrode 72 welded to the base 40 of the casing 38 in an appropriate location. The electrodes 66 and 72 serve as spark-ignition means.

In accordance with the present invention, a flame detector control device, indicated generally at 74, is mounted at the combustion air intake end of the air-fuel mixer casing 38, and projects axially into the air-fuel mixer casing 38 through the base 40. The control device 74 includes support means in the form of a generally L-shaped bracket 76 which is located within the air supply casing 12 and secured to the plate 28 by a screw 77. A switch 78, having a plunger 80, is disposed within the air supply casing 12 and is secured to the bracket 76 by means of screws 82. The switch 78 is adapted to be actuated by temperature responsive flame detector means 84- which is disposed in the air-fuel mixer casing 38 axially thereof and extends through the base 40 and the plate 28. The detector means 84 comprises a stainless steel tube 86 which, at its one end, is closed by a metal plug insert 88 and, at its other end, is secured in the bracket 76. Mounted within the tube 86 is a ceramic rod 90, the end 92 of which abuts the insert 88 and the end 94 of which engages a spring metal lever 96 intermediate of the ends thereof. One end of the lever 96 is anchored to the bracket 76 by a screw 98, and the other free end of the lever 96 engages the switch plunger 80. The lever 96, which serves as force transmitting means, moves the plunger 80' in a 2:1 ratio relative to movement of the rod 90.

The burner assembly is adapted to be mounted, as disclosed for example in United States Patent No. 2,990,- 877, in one end of a heat exchanger (not shown) of a vehicle heater or the like. The valve 22 is connected to a source of fuel (not shown), while the horn 26 is connected to a combustion air blower (not shown). A small portion of combustion air is transmitted from the casing 12 through the apertures 34 and opening 46 into the mixer casing 38. The larger remaining portion of combustion air is transmitted through the louvers 36 into the chamber 63 and then through the inlet holes 48 into the mixer casing 38. At the same time, fuel is sprayed by the nozzle through the opening 46 into the mixer casing 38. The ignition circuit of the spark plug 64 is closed and the spark at the electrodes 66 and 72 serves to ignite the combusti'ble air-fuel mixture. Hot products of combustion are discharged through the open end of the casing 38 into the associated heat exchanger from which the heat is exchanged to a ventilating air stream.

The two elements of the flame detector means 84- namely, the tube 86 and the rod 90-have substantially different coefllcients of thermo-expansion and hence are relatively axially translatable in response to changes in temperature within the air-fuel mixer casing 38. After the ignition circuit has been initially closed, and upon the development of a flame within the casing 38, the heat of the flame causes the stainless steel tube 86 to expand longitudinally, and the ceramic rod 90, which is not materially affected by heat and which is maintained in abutment with the insert 88 by reason of the spring metal lever 96, is moved away from the switch 78. This movement of the rod 90 effects a corresponding movement of the lever 96, and the switch plunger 80 is thereby permitted to move outwardly. Such operation of the switch deenergizes the heating coil of a time delay relay in the fuel valve circuit and at the same time energizes a holding circuit to permit operation of the combustion blower after the heater has been turned off. When the flame within the casing 38 goes out, the tube 86 cools and contracts causing the rod 90 to move toward the switch 78 thereby moving tht lever 96 and depressing the switch plunger 80 to actuate the switch 78 for energizing the heating coil of the time delay relay in the fuel valve circuit and otherwise restoring the associated circuitry to pre-start conditions. Because the flame detector control device 74 is mounted at the combustion air intake end of the air-fuel mixer casing 38, the installation of the device need not be sealed as has been required in prior construction.

While there has been shown and described a preferred embodiment of the present invention, it will be understood by those skilled in the art that various rearrangements and modifications may be made therein without departing from the spirit and scope of the invention.

I claim:

1. In a burner assembly including a cup-shaped air supply casing, a plate secured across the mouth of the air supply casing, a cup-shaped air-fuel mixer casing of smaller diameter than the air supply casing and having a base secured to the plate, a nozzle disposed Within the air supply casing and having an outer end projecting through the plate for supplying fuel to the air-fuel mixer casing through a central opening in the base thereof, the air-fuel mixer casing having air passageway means through the wall thereof, the plate having air passageway means therethrough radially outwardly of the air-fuel mixer casing, and enclosure means surrounding the air-fuel mixer casing and extending between the outer end of the latter and the outer periphery of the plate to form an annular chamber for receiving air from the air supply casing through the passageway means in the plate and transmitting the same into the air-fuel mixer casing through the passageway means in the wall of the latter, the improvement which comprises temperature responsive flame detector means disposed in the air-fuel mixer casing and extending through the base thereof and the plate, switch means disposed within the air supply casing and being actuatable by said detector means, and means within said air supply casing supporting said detector means and said switch means.

2. The improvement of claim 1 wherein said detector means is comprised of a tube with a closed end within the air-fuel mixer casing, a rod within said tube having one end in abutment with said closed end of said tube and having the other end extending through the base, and said tube and said rod having substantially different coeflicients of thermo-expansion; and wherein said switch means is cofinprised of a switch having a plunger actuata'ble by said r0 3. The improvement of claim 2 including a lever having its one end anchored to said supporting means and having its free end engageable with said plunger, and wherein said rod engages said lever intermediate of the ends thereof.

References Cited UNITED STATES PATENTS 1,828,692 10/1931 Townsend 158-28 2,195,649 4/1940 =Hallenbeck et a1. 158-28 2,482,551 9/1949 Korsgren 158-28 2,694,444 11/1954 Oldenkamp 158-28 JAMES W. WESTHAVER, Primary Examiner.

US. Cl. X.R. 

